[optimize] Reduce the memory used for comparing sequences of Item and Node objects

Author: adamretter

exist-core/src/main/java/org/exist/xquery/Except.java

@@ -82,7 +82,7 @@ public Sequence combine(final Sequence ls, final Sequence rs) throws XPathExcept
                 @Nullable Set<Item> set = null;
                 for (final SequenceIterator i = rs.unorderedIterator(); i.hasNext(); ) {
                     if (set == null) {
-                        set = new ObjectAVLTreeSet<>(new ItemComparator(null));
+                        set = new ObjectAVLTreeSet<>(ItemComparator.WITHOUT_COLLATOR);
                     }
                     set.add(i.nextItem());
                 }

exist-core/src/main/java/org/exist/xquery/Intersect.java

@@ -76,7 +76,7 @@ public Sequence combine(final Sequence ls, final Sequence rs) throws XPathExcept
                 @Nullable Set<Item> set = null;
                 for (final SequenceIterator i = ls.unorderedIterator(); i.hasNext(); ) {
                     if (set == null) {
-                        set = new ObjectAVLTreeSet<>(new ItemComparator(null));
+                        set = new ObjectAVLTreeSet<>(ItemComparator.WITHOUT_COLLATOR);
                     }
                     set.add(i.nextItem());
                 }

exist-core/src/main/java/org/exist/xquery/value/ArrayListValueSequence.java

@@ -267,7 +267,7 @@ public void removeDuplicates() {
         final List<Item> newValues = new ArrayList<>(values.size());
         int newType = Type.ANY_TYPE;
 
-        final ItemComparator itemComparator = new ItemComparator();
+        final ItemComparator itemComparator = ItemComparator.WITHOUT_COLLATOR;
 
         for (int i = 0; i < values.size(); i++) {
             final Item value = values.get(i);

exist-core/src/main/java/org/exist/xquery/value/AtomicValueComparator.java

@@ -48,11 +48,13 @@
 @ThreadSafe
 public class AtomicValueComparator implements Comparator<AtomicValue> {
 
-    protected static final Logger LOG = LogManager.getLogger(RESTServer.class);
+    protected static final Logger LOG = LogManager.getLogger(AtomicValueComparator.class);
+
+    public static AtomicValueComparator WITHOUT_COLLATOR = new AtomicValueComparator();
 
     private final @Nullable Collator collator;
 
-    public AtomicValueComparator() {
+    private AtomicValueComparator() {
         this(null);
     }
 

exist-core/src/main/java/org/exist/xquery/value/ItemComparator.java

@@ -56,6 +56,8 @@ public class ItemComparator implements Comparator<Item> {
     @Nullable private final Collator collator;
     @Nullable private AtomicValueComparator atomicValueComparator = null;
 
+    public static ItemComparator WITHOUT_COLLATOR = new ItemComparator();
+
     public ItemComparator() {
         this(null);
     }
@@ -70,7 +72,11 @@ public int compare(final Item n1, final Item n2) {
             return Constants.INFERIOR;
         } else if (n1 instanceof AtomicValue && n2 instanceof AtomicValue) {
             if (atomicValueComparator == null) {
-                atomicValueComparator = new AtomicValueComparator(collator);
+                if (collator == null) {
+                    atomicValueComparator = AtomicValueComparator.WITHOUT_COLLATOR;
+                } else {
+                    atomicValueComparator = new AtomicValueComparator(collator);
+                }
             }
             return atomicValueComparator.compare((AtomicValue)n1, (AtomicValue)n2);
         } else if (n1 instanceof Comparable) {

exist-core/src/main/java/org/exist/xquery/value/SequenceComparator.java

@@ -83,7 +83,11 @@ public int compare(final Sequence o1, final Sequence o2) {
 
         for (int i = 0; i < o1Count; i++) {
             if (itemComparator == null) {
-                itemComparator = new ItemComparator(collator);
+                if (collator == null) {
+                    itemComparator = ItemComparator.WITHOUT_COLLATOR;
+                } else {
+                    itemComparator = new ItemComparator(collator);
+                }
             }
 
             final Item i1 = o1.itemAt(i);

exist-core/src/main/java/org/exist/xquery/value/ValueSequence.java

@@ -500,7 +500,7 @@ private void removeDuplicateNodes() {
             if (!hasNodes) {
                 return;
             }
-            final Map<Item, Item> nodes = new TreeMap<>(new ItemComparator());
+            final Map<Item, Item> nodes = new TreeMap<>(ItemComparator.WITHOUT_COLLATOR);
             int j = 0;
             for (int i = 0; i <= size; i++) {
                 if (Type.subTypeOf(values[i].getType(), Type.NODE)) {